The long-term goal of this research is to build a better bridge between the tissue, cellular, and molecular levels of analysis of the frog embryo. The specific goal of this proposal is to probe the nature of molecular expression domains in the early embryo. The ability of pMRI to follow tissue movements and cell lineages in three dimensions over time in opaque specimens will be used, in conjunction with conventional molecular biology techniques, to map the lineages that contribute to a gene expression domain as well as the fates of the cells that were once within the domain. The specific hypothesis to be tested is that the gene expression domains are made up of dynamic populations of cells, requiring that cells express the marker gene as they enter a given domain, and extinguish it as they exit the domain. Towards this end, we will: (1) determine the normal lineages of cells that contribute to the frog nervous system. the axial mesoderm and the paraxial mesoderm: (2) determine the rel ationship between the early lineages and differential patterns of gene expression: (3) determine the changes in cell lineages and cell movements in perturbed embryos 1. Goal Directed Imaging: (a) provide comprehensive three-dimensional in vivo images of the developing brain in three different species (quail, mouse, and monkey) using Magnetic Resonance (MR) micro-imaging, (b) use fMRI techniques to examine how the visual field map of the owl monkey changes with increasing degree of myelination in brain of the young animal. 2. Analysis: (a) analyze the images at a number of different levels ranging from simple annotation to correlating the onset and developing organization of different structures in both space & time and to compare & contrast the avian, rodent, and mammalian systems. (b) mesh optical and MRI data of the same animal. 3. Dissemination: (a) make the images and tools for rendering & analysis available to the scientific community in a convenient format. e.g., photographs of 2D slices of the 3D data. CD-ROMs with annotated 2D and 3D images to be viewed using readily available software and software developed in-house. and an on-line database accessible via the World Wide Web where raw' as well as 'processed' data will potentially be available.